Kurdish fighters backed by US warplanes pushed back jihadists around Iraq's largest dam today, as Sunni Arab tribesmen and security forces fought the militants west of Baghdad.

Two months of violence have brought Iraq to the brink of breakup, and world powers relieved by the exit of divisive premier Nuri al-Maliki were sending aid to the hundreds of thousands who have fled their homes as well as arms to the Kurds.

Kurdish fighters were advancing on Mosul dam, which the Islamic State (IS) fighters seized a week ago, but their progress was being hampered by roadside bombs, Kurdish officials said.

The dam on the Tigris river north of Iraq's second city provides electricity and irrigation water for farming to much of the region.

It recapture would be the first major prize won back from the jihadists since they launched their shock offensive in early June, routing the security forces across much of northern and western Iraq.

An AFP journalist saw towers of smoke rising from the dam area today.

"Half of the Mosul dam area was retaken, the eastern part," said Kawa Khatari, an official of the autonomous Kurdish region's largest party.

"They are heading towards Tal Kayf, but the main road was planted with roadside bombs," he added.

Another Kurdish official, Harim Kamal Agha, said the bombs planted by the retreating jihadists were slowing the advance.

The US military said it carried out nine air strikes yesterday in support of Kurdish forces.

US Central Command said warplanes and drones had destroyed or damaged four armoured personnel carriers, seven armed vehicles, two Humvees and an armoured vehicle.

Buoyed by the air strikes US President Barack Obama ordered last week, Kurdish forces have tried to claw back the ground they have lost since the start of this month, when the jihadists went back on the offensive north, east and west of Mosul.

In Anbar province, west of Baghdad, security forces backed by Sunni Arab tribal militia, who threw their weight behind a counter-offensive against the jihadists on Friday, made gains west of the provincial capital Ramadi, police said.

Fighting was also taking place near the strategic Euphrates Valley town of Haditha, which hosts another important dam, Police Staff Major General Ahmed Sadag said.